Improvement in duplex chemical telegraphs



TLA. EDISON. Duplex Chemical Tele-graphs.

No.l56,8`43. Patented Nv.17,1v874.

4 JWM Q/ZWW @6M producing no effect upon the receiver.

UNITED STATES PATENT QEEIGE THOMAS A. EDISON, NEWARK, NEW JERSEY, ASSIGNOR'TO HIMSELF AND GEORGE HARRINGTON, OF WASHINGTON, DISTRICT OF COLUMBIA.

IMPROVEMENT IN DUPLEX CHEMICAL TELEGRAPHS.

Specification forming part of Letters Patent No. 156,84 3, dated November 17, 1874; application iiled March 13, 1873.

GAsE 69.

To all whom it may concern:

Be it known that I, THOMAS A. EDISON, of Newark, in the county of Essex and State of New Jersey, have invented an Improvement in Circuits for Chemical Telegraphs, of which the following is a specication:

The object of this invention is to transmit two dispatches over the same Wire at the same time by telegraphs employingperforated transmitting-paper and chemical receiving-paper.

I make use of apparatus for transmitting by perforated paper, and receiving the Inessages on chemical paper at the respective ends of the line, and employ batteries, resistances, and connections arranged in such a manner that the effect of the transmittingbattery shall be neutralized upon the receiving-instrument at the same end by an equalization of tensions, and the receiver shall be at a point Where the tension is equal to all the electric currents, except to that current which comes from the distant station.

In the diagram, d e are the receiving, and b c the transmitting, instruments. m n are the main batteries. -u and o are two batteries in the shunt-circuit opposing each other, and w w are batteries operating similar to a c. f g are resistance-coils, to increase and decrease the length of the shunt-circuits. h i are resistance-coils of nearly the resistance ot' the line. k l are the ground-plates. o p are the double contact-springs, one spring, 0, cutting off o r shortcircuiting77 the battery and the other spring, p, placing the main battery n upon the line. This main-battery current divides at df, part going on the line and part to theV ground, this route or negative of the battery through the resistance z' being in fact an artilcial line, it being Well known that a battery will supply several lines with an undiminished quantity of electricity, and that the addition of a line decreases the total resistance of the batterys circuit, and produces an eXtra amount of electricity.

To obtain the transmission of two messaitis only necessary that no eii'ect shall be obtained upon the4 receiving-instrument by the putting on of the sending-battery at the same station.

I will now describe how I produce this effect: When the paper of the message to be transmitted interven es between the contact-sprin gs q r and the drum b, :no current passes upon the line, and the batteries un, being balanced within .the shunt-circuit, produce no effect upon the receiver d, and a current coming from a distant station passes down the shunt, and also through the receiver d, and produces the message in the usual manner.

Supposing no current from the distant sta' tion was recording itself upon the receiver d, and it is desired to transmit a current to the distant station without producing any eect upon said receiver d, it is accomplished as' follows:

When the contact-springs q r are in metallic contact with the drum b, by passing into a perforation inthe paper being drawn over said drum, the current from the battery .m passes by r over the line, but it splits in three directions at c', part passing to the ground, and part passing by two routes to the line, via the shunt and the receiver d. The passage ofthe current through the receiver would give a large mark at the receiver were it not thatat the same time that the contact-sprin g r placed the battery m upon the line the spring q short-circuited the battery o, which had been opposing the battery a in the shunt, hence allowing said battery u to have free action, and the current from this battery thus set free acts in a contrary direction through the receiving-instrument d to that of the battery m, and by means of a switch for putting in and out more or less cups the power of the batteries m and u are neutralized on the chemical paper at d consequently no effect is produced at the receiver d when the battery m is placed on the line.

Of course, While the battery fm is on, if a currentV from the battery n is sent over the line it records itself in the usual manner upon the chemical paper on d.

I claim as my invention- 2 minste The local batteries u and n or w and n0` in Signed by me this 7th day of March, A. D. a shunt from the main line and opposingI 1873.

each other and a connection between them to the transmitting or receiving instrument, THOMAS A' EDISON' in combination with the main batteries, re- WVitnesses:

sistances, and circuits, arranged substantially GEO. T. PINCKNEY,

as and for the purposes set forth. I CHAs. H. SMITH. 

